Background Information on Loratadine
- Loratadine is a second-generation, non-sedating H1 antihistamine commonly used to treat allergic rhinitis and urticaria 1
- It is available in various formulations including tablets, oral solution (5mg/5mL), and is approved for patients 2 years and older 1
- Loratadine has a standard adult dose of 10mg once daily 1
- It is metabolized to descarboethoxyloratadine, which is four times more active than the parent drug 2
Pharmacological Properties
- Loratadine has high selectivity for peripheral histamine H1-receptors with minimal central nervous system effects 4
- Onset of action occurs within 1 hour and duration of effect is at least 24 hours, allowing for once-daily dosing 2
- Loratadine reaches peak plasma concentration in 1-2 hours; its main metabolite does so in 3-4 hours 2
- The elimination half-life is approximately 7.8 ± 4.2 hours for loratadine 1
- Unlike first-generation antihistamines, loratadine does not cause significant sedation at recommended doses 1
Clinical Considerations
- Loratadine (Claritin) is now available over-the-counter in the United States 5
- Its active metabolite, desloratadine, is marketed under the trade name Clarinex 5, 6
- Loratadine should be used with caution in patients with severe renal impairment 1
- At standard doses, loratadine does not cause sedation, unlike cetirizine (Zyrtec) which may cause mild drowsiness 1
- Loratadine has fewer anticholinergic effects compared to first-generation antihistamines 1
Comparison with Other Antihistamines
- Loratadine (Claritin) has been found to be as effective as terfenadine, clemastine, mequitazine and azatadine in relieving allergy symptoms 4
- It has a lower incidence of sedation compared to azatadine, clemastine, chlorpheniramine and mequitazine 4, 3
- Unlike some other second-generation antihistamines, serious ventricular arrhythmias have not been observed with loratadine 3
- Some patients who are dissatisfied with loratadine may find better symptom relief with desloratadine (Clarinex) or fexofenadine (Allegra) 5